In Meretz Investments NV and another v ACP Ltd and others - Butterworths Law Direct 11.12.07 the Court of Appeal considered the correct interpretation of the House of Lords' decision in OBG v Allan  4 All ER 545, in which it was held that there was a distinction between the torts of inducing a breach of contract and preventing its performance.
The Court of Appeal emphasised that on a true construction of the House of Lords’ authority, in prevention cases, the defendant did not join with the contracting party in a wrong committed by the contracting party, with the result that tortious liability did not arise in prevention cases unless the preventative means used were independently unlawful. Where a party did something which he was entitled to do because of his contractual right conferred by A, the fact that it resulted in a breach of B's contract with A could not constitute unlawful means of which A could complain in an action for damages for unlawful means conspiracy. The court had to look at the whole of the means used by the alleged tortfeasor and not simply its effect on the party rendered in breach.
This was a prevention case. It therefore had to be shown that the preventative means used by the second Defendant were 'independently unlawful'. That could not be done because the second Defendant was contractually entitled as against the first and second Claimants to exercise its power of sale. The claim for conspiracy also failed on the ground of lack of unlawful means